Problem with slave server

Hi,
I currently have 3 servers running OPENLdap (2.1.25-6) from Mandrake 10
The Master and one of the slaves run happily, however the 2nd slave keeps
giving me these errors when i start up:
slapd[15105]: ldbm: ==> unable to initialize mutex: Function not implemented
slapd[15105]: ldbm: ==> process-private: unable to initialize environment
lock: Function not implemented
slapd[15105]: ldbm_initialize_env(): FATAL error in dbEnv->open() :
Function not implemented (38)
Anyone seen this before? Even better, anyone able to suggest a way to
overcome it?
Thanks in advance
Chris